Journal article


JR Callingham, BM Gaensler, RD Ekers, SJ Tingay, RB Wayth, J Morgan, G Bernardi, ME Bell, R Bhat, JD Bowman, F Briggs, RJ Cappallo, AA Deshpande, A Ewall-Wice, L Feng, LJ Greenhill, BJ Hazelton, L Hindson, N Hurley-Walker, DC Jacobs Show all



We present broadband observations and spectral modeling of PKS B0008-421 and identify it as an extreme gigahertz-peaked spectrum (GPS) source. PKS B0008-421 is characterized by the steepest known spectral slope below the turnover, close to the theoretical limit of synchrotron self-absorption, and the smallest known spectral width of any GPS source. Spectral coverage of the source spans from 0.118 to 22 GHz, which includes data from the Murchison Widefield Array and the wide bandpass receivers on the Australia Telescope Compact Array. We have implemented a Bayesian inference model fitting routine to fit the data with internal free-free absorption (FFA), single- and double-component FFA in an ..

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Awarded by U.S. National Science Foundation

Awarded by Australian Research Council (LIEF)

Awarded by U.S. Air Force Office of Scientific Research

Awarded by Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence

Awarded by Victoria University of Wellington (via grant from the New Zealand Ministry of Economic Development)

Funding Acknowledgements

The authors thank Geoffrey Bicknell, David Jauncey, and Edward King for stimulating discussions about the theoretical aspects of the absorption models and the VLBI measurements of PKS B0008-421. This scientific work makes use of the Murchison Radioastronomy Observatory, operated by CSIRO. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the MWA comes from the U.S. National Science Foundation (grants AST-0457585, PHY-0835713, CAREER-0847753, and AST-0908884), the Australian Research Council (LIEF grants LE0775621 and LE0882938), the U.S. Air Force Office of Scientific Research (grant FA9550-0510247), and the Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence funded by grant CE110001020). Support is also provided by the Smithsonian Astrophysical Observatory, the MIT School of Science, the Raman Research Institute, the Australian National University, and the Victoria University of Wellington (via grant MED-E1799 from the New Zealand Ministry of Economic Development and an IBM Shared University Research Grant). The Australian federal government provides additional support via the CSIRO, National Collaborative Research Infrastructure Strategy, Education Investment Fund, the Australia India Strategic Research Fund, and Astronomy Australia Limited, under contract to Curtin University. We acknowledge the iVEC Petabyte Data Store, the Initiative in Innovative Computing. and the CUDA Center for Excellence sponsored by NVIDIA at Harvard University, and the International Centre for Radio Astronomy Research (ICRAR), a Joint Venture of Curtin University and the University of Western Australia, funded by the Western Australian State government. The Australia Telescope Compact Array is part of the Australia Telescope National Facility, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This paper includes archived data obtained through the Australia Telescope Online Archive ( This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.